Iran has claimed it has arrested the "main elements" behind the assassination of two of its nuclear scientists, alleging they were spies working for Israel.

The intelligence ministry said on Thursday it had identified a number of agents affiliated with the "Zionist regime" involved in the January assassination of Mostafa Ahmadi Roshan, a key figure at one of Iran's main uranium-enrichment facilities and the 2010 killing of Majid Shariari, a senior nuclear scientist.

Local news agencies published what appears to be a terse statement by the ministry, which does not shed light on the numbers, names or nationalities of those said to be detained nor clarifies where and when they were arrested.

"A series of heavy and thorough intelligence operations which begun after the assassination of our first nuclear scientists … led to the identification of a number of agents [gathering information] for the fake regime that rules over the occupied territories," it said.

In January, attackers on a motorbike stuck a magnetic bomb to a car carrying Roshan, deputy director of the Natanz plant. The car's driver, Reza Ghashghaee, was also killed in the attack, which took place during morning rush-hour in Tehran.

Roshan was the latest victim in what is widely seen as a covert war against the Islamic republic's nuclear programme. It was the fifth assassination of an Iranian nuclear scientist in the past two years.

Shariari, a member of the nuclear engineering faculty at Tehran's Shahid Beheshti University, was killed in November 2010 when bomb attacks targeted two Iranian nuclear scientists.

Shahriari was killed. His colleague, Fereidoun Abbasi-Davani, who was wounded in the attack, was later promoted as head of the country's atomic energy agency.

Shahriari and Abbasi-Davani were targeted by attackers on motorcycles who attached bombs to the victims' cars.

In recent years, Iran's nuclear programme has experienced setbacks including the assassination of its scientists and the release of the Stuxnet computer worm, designed to sabotage its atomic facilities and halt its enrichment programme. The malware is believed to have targeted a control system used in Iran's nuclear sites in July 2010.

Embarrassed domestically by the inability to protect its scientists, Iran claims it has launched various sophisticated operations to identify the culprits.

In May this year, Iran hanged 26-year-old Majid Jamali Fashi, who the authorities alleged was responsible for the assassination of Masoud Ali-Mohammadi, a particle physicist killed in January 2010.

According to Iran, Jamali-Fashi confessed to having attached a remote-controlled bomb to a motorcycle parked on the street, which detonated and killed Ali-Mohammadi while he was leaving home for work. The extent of Ali-Mohammadi's involvement in the country's nuclear programme is unclear.

In the face of little independent information available on Jamali-Fashi, observers have questioned whether he was involved in the killing of Ali-Mohammadi. Some suspect Iran is struggling to cover its embarrassment at home by staging a series of show trials and claims of arrests.

Iran says its nuclear activities are peaceful and has accused the west – the US and Israel in particular – of attempting to prevent Tehran from acquiring a technology it claims to want for medical and energy supply purposes.

The west fears Iran's nuclear programme may have military applications and has imposed sanctions to force the authorities to permit the International Atomic Energy Agency inspectors full access to its nuclear sites.

Iran is due to hold nuclear talks with the world's major powers in Moscow next week, when its top officials meet their counterparts from the US, France, Germany, China, Russia and Britain, the group known as P5+1.